This invention relates to a device for attenuating noise generated by a pressurized fluid when released to the atmosphere, especially steam, for example from a geothermal power plant.
Rock-filled type mufflers have been used for attenuating noise generated by pressurized steam upon release to the atmosphere. These mufflers generally consist of a container filled with rock aggregate, typically of 1-6 inch screening. The pressurized steam is introduced at or near the bottom of the container, passes through the body of the aggregate and exits from the surface. In general, the fill is not held in place by a screen or grill because a failure could cause a sudden dangerous ejection of hot rock. In order to prevent ejection of the fill, therefore, conventional rock-filled mufflers are made very large to accommodate steam surges and hence are very costly and difficult to site.
One alternative to the conventional rock filled muffler is disclosed in U.S. Pat. No. 4,353,434, the disclosure of which is incorporated herein by reference. In that muffler, a pressurized fluid stream is introduced via a distributor into a basal or lateral compartment of the container which is separated from the rock fill by a perforated element made of masonry, concrete, wire mesh, metal plate or metal grid. A portion of the pressurized fluid flows through the fill to the atmosphere, and a portion flows from the fill into a void volume formed within the fill before exiting the muffler.
Blow off mufflers that flow steam past fiber-filled baffles usually provide adequate silencing but have high cost and potentially poor longevity. Compact particle-filled mufflers, in contrast, have excellent longevity and modest cost, but only modest noise reduction, so have seen relatively little use.